Crop Adaptation to Climate Change (Yadav/Crop Adaptation to Climate Change) || Research from the Past to the Future

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Chapter 29

Research from the Past to the FutureEC (Ted) Wolfe

Introduction

The context for this chapter is the history of andresults from crop improvement, from the earlydomestication of useful crops to the present.Progress has occurred during successive phasesof development (Table 29.1), beginning with thediscovery of useful plant types, their domesti-cation as early as 8600–8000 BC (Zohary andHopf 2000), and their spread to new locations.Progress continued with the selection of utilitar-ian plant traits by farmers and seedsmen, beforean era of scientifically based crop improvementthat began in the nineteenth century. At present,there is a vigorous application of specific disci-plines (genetics, biotechnology, statistics, and in-formation systems) to plant breeding processes.

The main topic of the chapter is an analysisof factors necessary to ensure that plant scienceis holistically, realistically, and advantageouslyplaced to meet the demands of the future. Thescale of these demands is toward a historic crisisin producing food for the increasing world pop-ulation. This population may increase by 40%over the next 40 years. By 2050, the level offood insufficiency will depend on the extent ofclimate change, population trends, resource con-straints, and trends in crop production.

In this chapter, future gains in plant scienceand crop production are considered from twoperspectives. The first is a disciplinary overviewof the history of crop improvement, one thatcompares the possibilities for ”great leaps for-ward” along with the continuation of incremen-tal progress in plant breeding. This overview isbased on the available literature and partially onthe chapters of this book. These chapters consti-tute a timely analysis of the effects of climate oncrop genotypes and the way forward, involving abroad array of physiological pathways and plantbreeding approaches.

The second perspective is more complicatedand less exact. It is a consideration of princi-ples that are evident at higher levels of ecosys-tem organization, where studies of organismsand processes at the cellular or disciplinary lev-els become confounded by the complexity ofinteracting components and limiting factors atthe ecosystem level (Giampietro 1994, 2004).Such complexity goes beyond the plant sciencedisciplines, encompassing real-world constraintssuch as the availability of research funds; syner-gism and antagonism in research including rela-tionships within and between private and publicinstitutions; the future availability of essentialresources such as land, fertilizer, and energy; the

Crop Adaptation to Climate Change, First Edition. Edited by Shyam S. Yadav, Robert J. Redden, Jerry L. Hatfield,Hermann Lotze-Campen and Anthony E. Hall.c© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd.

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RESEARCH FROM THE PAST TO THE FUTURE 557

Table 29.1. A brief history of plant improvement.

PhasesExamples of crops, processes, and activities along the pathway tocommercialization

Domestication and selection � Wild forms of wheat (Triticum spp.) were grown in Mesopatamia as earlyas 20,000 years ago, brought into cultivation through the selection ofmaterials that were not shattering, nondormant, large-seeded, evenripening, lighter color, and better-tasting. Dispersed along trade routes intoEurope.

� Maize (Zea mays), originating in Mesoamerica around 10,000 years ago,spread through the Americas as a food staple, then worldwide.

International trade � The culture of coffee (Coffea spp.) began in Ethiopia, thence to the ArabianPeninsula (1100 ad) where the roasting/boiling recipes were perfected topopularize coffee. In the early 1700s, coffee beans/plants weresurreptitiously introduced to Latin America (early 1700s) and othergeographical areas. Tea, originating in China, had a similar history.

� Potato (Solanum tuberosum), domesticated in Peru-Chile between 3000 bcand 2000 bc; introduced to Europe (fifteenth century), Asia (sixteenth toseventeenth centuries), Africa (twentieth century).

Genetics and purposeful plantbreeding

� This phase includes the deliberate collection, conservation, and storage ofuseful crop plants and their progenitors (land races, wild relatives),beginning with plant collection expeditions of early civilizations andculminating in a network of international plant genetic resource centers(CGIAR network established in 1974).

� The purposeful improvement of crop plants by propagation, crossbreeding,and selection for desirable traits began as a science during the past twocenturies, following on from the pioneering work and publications ofMendel and Darwin in the mid-nineteenth century.

Hybridization � Natural hybridization occurred in the development of tetraploid durum(Triticum durum, AABB, 2n = 28) and Timopheev wheats (Triticumturgidum, AAGG, 2n = 28) and hexaploid bread wheat (Triticumaestivum, AABBDD, 2n = 42).

� In maize, the morphology of this monecious plant (terminal male florets onthe main stem, female florets on cobs in axillary and lateral positions) issuitable for the exploitation of plant hybrids to simplify breeding and gainfrom heterosis.

The green revolutionThe ecogreen revolution

� Refers to the introduction and widespread use of dwarfing genes to enhancethe standability and harvest index of wheat and rice varieties. Greatprogress was made during the 1960s and 1970s. Followed by an “ecogreenrevolution” (Swaminathan 2006) in which crop management was refined toreduce adverse environmental effects and to ensure social equitability.

� Broadening of the base of useful crops such as legumes to providebiologically fixed nitrogen. For example, the production of sweet lupinvarieties for use in Western Australia from the 1970s (Gladstones 1970).

The biotechnology era � DNA extraction and amplification (PCR). The developing sciences ofmolecular genetics (genomics, transgenics, genetic markers) provide newtools for plant breeders.

Future innovation � Marker-assisted plant breeding and strategic releases of transgenic crops.



558 CROP ADAPTATION TO CLIMATE CHANGE

human resources that are available for farming;and the expectations of consumers with regardto the availability and quality of food and fiberderived from crops.

An overview of the historyof crop improvement

An overview of the phases of crop domestication,development, and use is contained in Table 29.1.The phases (rows in the table) are arranged fromthe earliest (top) to the most recent (bottom) butthere is overlap between the phases to greater andlesser extents. The early history of crop plantswas dominated by the discovery of useful newcrops, such as wheat in the Near East, maizein Central America, potato in South America,and soybean in China. Following those discov-eries, plans (sometimes ambitious, occasionallysecret) were usually made for the transport ofseeds, cuttings, or whole plants of specific cropsto new locations that were suitable, climaticallyand strategically, for the culture of these crops.Thus, maize became a major crop in south andeast Africa, potato in Europe, soybean and wheatin the America, cassava in West Africa, rubberin Malaya, and tea in India. With the progressionin climate change, further shifts in crop typesmay become necessary from region to regionand country to country.

Advances in plant breeding occur from suc-cessive cycles of introduction, crossing, and se-lection in order to achieve vigor, reduce dis-ease, and adapt to new habitats and uses. Break-throughs in plant breeding (Khush 2005) are rarebut they do occur both deliberately (see the ex-amples in the following section) and sometimesfortuitously (e.g., the discovery of colchicinesfor doubling chromosome number). Plant breed-ers have now gone beyond the early “low hang-ing fruit” approach toward a state where theirbreeding aims, models, and strategies are con-tinuously refined in order to increase their likeli-hood of success. Although in past decades it wassuggested1 that 90% of the gain in plant breed-ing was produced by 10% of the plant geneti-

cists and breeders (the idea of leaders and fol-lowers), modern plant breeding activities havebecome better integrated, nationally and glob-ally, through improvements in communicationand intra-/interdisciplinary cooperation.

The preceding chapters of this book provideseveral perspectives for enhancing the productiv-ity of crops, such as the potential for overcomingthe limitations to temperate crops of the C3 pho-tosynthetic pathway (see, for example, Chapters12 and 16 of this volume, for rice and cowpea,respectively). The reader needs to explore theseperspectives, written by authors who rely on theirprofessional analysis of the patterns and gapsevident in past progress, plus their knowledgeof new scientific technologies and innovations,to increase the likelihood of disciplinary break-throughs and/or incremental gains.

Inspiring breakthroughsin plant science

Schiere et al. (2006) emphasized the importanceof events and processes in agriculture that in-teract rather than behave in a straightforwardmanner. Plant scientists and farmers need tobe more aware of the potential of these inter-actions that may trigger “nonlinear paradigmshifts” or “mode changes” in agriculture. Duringthe twentieth century, rapid rather than incre-mental changes were triggered by events suchas the “dustbowl” era on the North AmericanGreat Plains, high wool prices and pasture im-provement technologies during the 1950s in Aus-tralia, and economic reforms in China during latetwentieth century. Future perturbations to worldagriculture may arise from not only rapid climatechange but also sudden fuel shortages or changesin government policies, which may require ma-jor changes to the agricultural systems of wholecountries. Plant breeding can be imagined inthese terms, with certain genetic breakthroughsproducing paradigm shifts in food production,shifts that contrast with the more usual patternof progress in plant breeding and application.




This pattern is characteristically steady andsometimes frustratingly slow.

An obvious example of a mode of change isthe “Green Revolution”, which was based on theintroduction of dwarfing genes into cereal crops.In wheat, the dwarfing alleles Rht-B1b (or Rht 1)and Rht-D1b (Rht 2) were sourced from theJapanese variety Daruma and perpetuated bythe Norin 10-Brevor 14 crossbred; in rice, thedwarfing gene from a Chinese cultivar “Dee-gee-woo-gen” was a feature of the crossbreeds TN-1(Taiwan) and IR-8 (IRRI-Philippines). Thesedwarfing genes, which impair the biosynthesis ofthe growth hormone gibberellin (Hedden 2003),produced semidwarf plants that not only directedmore assimilate to the grain component of thecrop (i.e., the plants had an inherently higherharvest index) but also were physically more ca-pable of supporting a heavy grain crop (i.e. re-sistant to lodging).

The boost in crop yields from the semidwarfcultivars also depended on the application ofhigher levels of fertilizer, water, and pesticides,which at the farm level was encouraged by a mas-sive extension campaign. However, the combi-nation of high-yielding genotypes and increasedinputs caused adverse changes in the biologicalbalance, including the depletion of soil nutrientsand groundwater resources, the application ofexcess levels of fertilizers that caused pollutionand eutrophication, and an increased susceptibil-ity to diseases and pests as a consequence of aless diverse genetic base.

Hence, the Green Revolution of the 1960sand 1970s eventually swung more toward theconcept of an “Evergreen Revolution” (Swami-nathan 2006), in which the new technologieswere implemented in a manner that was moreacceptable, environmentally and socially. Theseobjectives entailed matching fertilizer and chem-ical applications to crop requirements, adopt-ing integrated pest and disease managementstrategies, involving the farmers in co-learningprocesses, and improving the access of small-holders to credit. The process of achievinghigher yields in a more sustainable and equi-

table manner is an ongoing one—as noted bySwaminathan (2006), there must be synergy be-tween science and public policy to alleviatehunger.

Another interesting example of the impor-tance of collaboration between disciplines is theaccount of Busch et al. (1994) concerning theconversion by Canadian scientists of rapeseed(Brassica napus = B. campestris and B. rapa)to canola. The market for rapeseed oil, a steamengine lubricant that contains high levels of eru-cic acid (C22 : 1), collapsed after World War IIwith the widespread replacement of steam-powered marine and locomotive engines withdiesel engines. The pathway toward a new food-oil crop required a change in the composition ofthe oil component from the unpalatable erucicacid (which was potentially threatening to hu-man heart function) to oleic acid (C18 : 1), plusthe removal of glucosinolate compounds (goitro-genic to pigs and chickens) that contaminatedthe meal portion of the oilseed. This transfor-mation journey, from the mid-1950s to the late1970s and beyond, was based on an understand-ing of the genes responsible for oil composi-tion. However, success depended also on othercrucial components, such as important devel-opments in gas–liquid chromatography that re-duced the volume of oil needed for assay fromseveral liters to a few milligrams, and an un-derstanding of the nutritional properties of oiland meals for humans and farm animals. Bythe 1980s, Canadian farmers had a crop that ri-valed the versatility of soybeans grown in theUnited States.

Once canola was available, the cycle of in-novation continued. The inclusion of a canolacrop in crop rotations was demonstrated to bebeneficial to the following wheat or barley crop,due to the break in the life cycle and levels ofsoil pathogens, reducing the incidence of cerealroot rots in both Canada (Bourgeois and Entz1996) and Australia (Angus et al. 1999). At atime of considerable world investment in thenew technologies of molecular biology to under-take further genetic transformations in oilseeds




(soybean, sunflower, Brassica, and peanut—Burton et al. 2004), Canada concentrated onBrassica crops (Scarth and Tang 2006) and, toa lesser extent, on linola/flax (Linum usitatis-simum). In Brassica, natural or induced muta-tions produced crops with altered levels of eru-cic acid, oleic acid, and linolenic acid (C18 :3). Gene transfer was involved in the productionof canola with a high proportion of lauric acid(C12 : 0), the world’s first transgenic commer-cial oilseed. Then followed several other Bras-sica genotypes with novel genes for oil com-position (Scarth and Tang 2006), herbicide re-sistance and the production of hybrid seed. InAustralia, during the 1990s, the popularity ofcanola stimulated the use of lime to correct soilacidity of many croplands, and these limed soilswere also beneficial for the establishment oflucerne (alfalfa) for the pasture phase in croprotations.

Another important example of a technologi-cal breakthrough in the 1990s was the transferto cotton of the Bt gene and the Roundup-Readytrait, a development that was crucial in the in-tegrated pest and weed management programsthat are now features of Australian and worldcotton production (Knox et al. 2006; Werth et al.2006). Bt cotton in particular was a crucial de-velopment due to the development of resistanceby key insect pests to a succession of chemicalinsecticides.

These examples of success contrast with thetortured history of commercialization of geneti-cally modified crops in many countries, includ-ing Australia. Skerritt (2004) provided a com-prehensive summary of the ongoing discussionsbetween science, industry, and society that havedelayed or thwarted the commercialization oftransgenic or genetically modified (GM) crops.However, even that account falls short of ex-plaining either the deep suspicion of Europeanpeople toward any tampering with the integrity oftheir food supply or the antagonism of Europeanagribusiness interests, which initially felt threat-ened by North American agribusiness firms thatpioneered the GM technology. Subsequently, the

debate has ebbed and flowed, with GM cropsnot gaining much of a foothold in many Euro-pean countries (France, Germany) and Australia.Christoph et al. (2008) concluded that consumerswho oppose genetic modification lack trust in au-thorities, industry, and scientists. Skerritt (2004)remarked that “The opposition to GM crops isconfusing to many scientists, who through theirtraining use reason rather than perceptions tocome to conclusions and thus in some cases(they) can be dismissive of social process andperceptions”. Much to the chagrin of the propo-nents of GM, campaigns to educate consumerswill not necessarily cause more support for GMcrops, because additional knowledge can gen-erate opposition as well as support (Christophet al. 2008). The response of producers is simi-lar. Producer groups and consumer groups, withthe opportunity of choice, will exercise thatchoice. Perhaps the influential opponents of GMtechnology will selectively accept innovationonly when the choices become starker, such asproducing a profitable or an unprofitable cropand/or having sufficient or insufficient suppliesof food.

Hence, in summary, paradigm shifts of thetype referred to by Schiere et al. (2006) have onlypartially occurred so far in the case of GM crops;the overall response is underwhelming com-pared with the extravagant claims and counter-claims made by both the techno-positivist andenviro-pessimist sectors of society. However,the work of scientists at the cell and molecu-lar levels is finding application in plant breed-ing (see case studies A and E below). Agricul-tural development at various scales (paddock,farm, regional, or national) is most balanced andsuccessful when principles and research find-ings from the disciplines of plant breeding andagronomy are combined with other disciplinesfrom the domains of environmental scienceand social science. This necessary collabora-tion should be borne in mind when readingearlier chapters, which are written naturallyenough from a reductionist rather than a systemicperspective.




Incremental advances in plantbreeding—the hard slog

A number of books and papers have presentedthe historical trends in crop yields (t/ha). Thesereports have highlighted a continuous upwardtrend in crop yields. For example, Egli (2008)summarized progress in corn and soybean yieldin the United States, noting in corn a five-fold increase in average yields during the cen-tury from the founding date of the Ameri-can Society of Agronomy (1907) (1706 kg/ha)to 2005 (9300 kg/ha). In 2009, average US maizeyields reached a historical high of 10.2 t/ha.Similarly, US soybean yields rose approximatelyfourfold over the period from 1924 (739 kg/ha)to 2005 (2909 kg/ha). Both Egli (2008) and At-ack et al. (2009) provided several examples of“hockey stick” yield curves of various crops inthe favorable US environment—a slow increasein crop yields up until the 1950s, when a morerapid linear trend began. Egli (2008) attributedthe rapid phase to a dramatic shift from a low-to a high-input production system that includesnew hybrid cultivars, a rapid escalation in theuse of N fertilizer on corn, better weed controlusing herbicides, mechanization (timely sowing,increases in plant population), and specializationtoward the dominant corn-soybean rotation. At-ack et al. (2009) took a broader view of agricul-tural innovation in the twentieth century, addingdevelopments in plant protection, grain protec-tion, finance/marketing and logistics to the ge-netic, fertilizer, and mechanical advances.

In England, also, the average yield of wheatincreased steadily during 750 years, from 0.5 t/hain the first half of the thirteenth century to3.4 t/ha in the third-quarter of the twentieth cen-tury; it currently stands at >8 t/ha. In the Euro-pean Union, postwar yield trends were linearlypositive in most countries for the main crops, es-pecially wheat and barley (Chloupek et al. 2004).Chloupek et al. (2004) attributed yield improve-ment to optimization of many factors, inclusionof varieties, fertilization, plant protection, andwarmer seasons.

Even in the marginal environment for wheatproduction in Australia, where average wheatyields declined toward 500 kg/ha in 1900 dueto nutrient exhaustion and crop diseases, yieldincreases during the next century were up-ward during and across each of three steppedphases—1900 to 1950 (with average nationalwheat yields rising to a new plateau of 800 kg/hadue to new cultivars, superphosphate fertilizer,and water conservation); 1950 to 1990 (1.4 t/ha,due to better varieties, legume nitrogen, andtimely sowing; and from 1990 to 2000 (2.0 t/ha,due to break crops, N fertilizer, and no tillage)(Angus 2001).

In summary, the recent history of world cropyields has been one of near-linear increases overthe last 5–8 decades, with no conclusive evidenceof a decline in the rate of yield improvement asyet. However, ongoing forward projections (Har-ris and Kennedy 1999, Gilland 2002, Keating andCarberry 2010) indicate the difficulty of match-ing food supply to population growth by 2050,with estimates of food production in particularbeing based on arguable assumptions.

What are the future prospects for the contin-uation of the upward trend in crop yields? Toadd to the individual perspectives included inthis book, I used the world literature to evalu-ate progress toward some specific objectives incrops. These evaluations are summarized in thecase studies A to E below:

� Case study A: Drought tolerance improvementin crop plants. Improving the tolerance of wa-ter stress for dryland crops is a strategic ob-jective of prime importance. Cattivelli et al.(2008) outlined an integrated approach to im-proving traits that reduce the gap betweenpotential and actual crop yields in drought-prone environments. First, they argued thatselection for high yield in stress-free envi-ronments has indirectly improved yield inwater-limiting situations. Second, a numberof physiological traits (stomatal conductance,time of flowering, the stay-green characteris-tic, and osmotic adjustment) are known to be




relevant to drought conditions. Third, selectionfor drought tolerance is poised to become moreefficient due to the application of QTL (quan-titative trait loci) analysis, making available anumber of markers that are tightly linked toloci for stress-related traits. Progress could beslow because of the number of genes involved,the interactions among them, and the pre-cision required for marker-assisted selection(MAS) of drought tolerant QTLs. Cattivelliet al. (2008) concluded that genomics-assistedbreeding had so far made only a marginal con-tribution to selecting drought-tolerant geno-types, but the way forward for research (dis-covery of physiological traits, identifying fa-vorable loci, MAS, gene cloning and insertion,elite genotypes, and field validation) is clear.

� Case study B: Drought tolerance and wateruse efficiency in rice. A series of recent ar-ticles in Advances in Agronomy (Wassmannet al. 2009a and 2009b, Farooq et al. 2009,Serraj et al. 2009) targeted strategies to en-hance the adaptation of rice to climatic stress.The general tone of these publications is op-timistic in terms of manipulating physiologi-cal mechanisms of stress tolerance/avoidance,adjusting crop management, tuning irrigationsystems toward a more efficient use of water,and enhancing the adoption of innovations byfarmers. However, as is noted in Chapter 12 ofthis book:� the effects of CO2 and higher temperatures

on rice plants grown in cool temperate areasare likely to be different from those in warmareas, and

� the future CO2-rich, warmer environmentwill affect other field parameters such ashumidity levels and soil nitrogen content.

The development and field validation of ro-bust air-plant models and plant-soil models forrice and other crops are major challenges toagricultural scientists, challenges that urgentlyrequire inputs from environmental scientists. Itis important that the historical standoff betweenthese respective silos of science is resolved, en-

abling new partnerships that contribute to thefuture of managed systems (including human so-ciety) as well as natural ecosystems.

� Case study C: Improving tolerance of heatstress in cotton. From the literature reviewedby Singh et al. (2007), it is expected that ris-ing temperatures will exert a negative influ-ence on the crop growth rate, photosynthesis,phenology, and yield of world cotton crops,most of which are nearing the limit of high-temperature tolerance. Aside from the issueof water availability, rising temperatures in-terfere with the interception and absorptionof photosynthetically active radiation, as wellas increase dark respiration. The pathway to-ward heat tolerance in cotton is not clear cut,with much genetic, physiological, biochemi-cal, and field work needed before additionalheat-tolerance traits can be identified and uti-lized (Singh et al. 2007). Hence, breedingfor high-temperature tolerance in cotton, us-ing traits such as stomatal water conductance(heat avoidance), smaller and thicker leaves,and flowering dynamics at high temperatures,is likely to be characterized by incrementalprogress rather than rapid advances.

� Case study D: Genetically based variation inN2 fixation has been demonstrated for soy-bean and other legume species but incorpo-rating such variation into cultivars has hadlittle success (Herridge and Rose 2000). Inhindsight, these authors reasoned that theirchances of success were low since the N2

fixation trait must be combined with severalother desired traits, and it is difficult to assessin large breeding populations. They suggestedthat soybean breeders should be encouraged toconduct their entire programs in low N2 soils.

� Case study E: Flowers and Flowers (2005)considered the question “Why does salin-ity pose such a difficult problem for plantbreeders?”. Enhancing the salt tolerance ofplants, particularly for use in delta regions,has met with limited success due to thecomplexity of the trait, both genetically and




physiologically. For example, according toFlower and Flower (2005), salt tolerance inplants depends on plant and leaf morphology,compartmentation (salt storage in vacuoles),the presence of organic solutes that protectplant metabolism, regulation of transpiration,control of ion movement, membrane charac-teristics, and tolerance of high Na/K ratios inthe cytoplasm. Several of the underlying phys-iological processes are not well understood.The genetic control of the quantitative traitof ”salt tolerance” is multigenic and, further,the putative markers for each loci involved aresensitive to the conditions under which plantsare grown. While there have been some suc-cesses in mapping salt-tolerant traits using aQTL approach (e.g., Lindsay et al. 2004, se-lecting genotypes with low Na+ accumulationin wheat), thereby opening the way for MAS,the overall utility of the approach has yet to beconfirmed. One complication is that genotypesthat survive by excluding salt may worsen thesalt content of the growing environment.

In summary, these are challenging times forplant physiologists, geneticists, and plant breed-ers. For major crops such as rice, wheat, andmaize, with integrated teams of plant scientistsbuilding up a wealth of information and work-ing internationally to a set of clear objectives,the likelihood of both occasional breakthroughsand steady progress is high. Even research intohuman genomics may produce dividends forplant scientists. Spillover benefits are likely frommajor crops to lesser crops, and from environ-mental science to agricultural science. However,research progress depends on maintaining or in-creasing investment from private/public sourcesas well as ensuring effective, unselfish collabo-ration.

The potential of biotechnology

At this point, it is worthwhile to consider thefuture potential of biotechnology (= molec-ular biology, bioengineering) applications forplant species improvement. Biotechnology is

justifiable on the basis that it has the po-tential (1) to achieve what conventional plantbreeding might never achieve and (2) to en-hance the efficiency of the plant breeding pro-cess itself, primarily through MAS. Spangenberget al. (2001) outlined a number of opportunitiesand approaches for the application of transgenicand genomic technologies for the improvementof forage plants, while Langridge and Gilbert(2008) realistically appraised the prospects ofgenetic technologies to effect further improve-ments in the yield and quality of cereals. In anumber of chapters in this book, examples aregiven of the potential for marker-assisted plantbreeding. Beyond the practical realm of MAStoward the ideal of gene insertion, biotechnolo-gists have often expressed unrealistic optimismin terms of achieving, on-time and on-budget,the targets that they or their backers set (e.g., thesearch for salt- and cold-tolerant crops). In themajority of cases, the pathway from the cell tothe ecosystem level may be impossibly difficultunless there are known functional relationshipsthat link gene function to plant physiology andfield performance (Hammer et al. 2008). The sci-entific understanding of the plant genome is stillpoor—substantial effort will be needed to as-sign function to genes, particularly when proteinfunction is context dependent.

Even in the case of single gene transforma-tions where plant phenotypic response scalesdirectly from the molecular level (e.g., the Btgene), there is a complex sequence of steps nec-essary to insert the gene, alter its level of expres-sion and utilize it (Oram and Lodge 2003). Theexperience of Dear et al. (2003) with transgenicsubterranean clover is revealing. A gene for tol-erance to bromoxynil herbicide (bxn) was iso-lated from a soil bacterium and inserted success-fully into a range of agricultural plants, amongthem subterranean clover (a pasture legume).Dear and his colleagues explored some of thepotential changes that a random insertion of thebxn gene might cause. The inclusion of the bxngene did not change the agronomic characteris-tics of one of the three resultant lines, but the gene




or transformation process did have unintendedeffects (reduced seed production, lower levels ofhard seed, and changes to the levels of phyto-oestrogens) on the other two transgenic lines.

The pathway to commercialization is long,involving a considerable regulatory burden toensure full deregulation of a GM product (Lan-gridge and Gilbert 2008). However, there are sev-eral public-private plant breeding groups, work-ing with a major species for the world market,that possess sufficient expertise and experiencefor success at the genome, plant, and industrylevels. Such groups will utilize molecular markertechnologies that are useful in exploring plantgenomes and in building up genetic combina-tions for yield and disease resistance. A goodexample of such an approach was recently re-ported by Kolmer et al. (2008), who identifiedan allele (csLV34b) that has a strong associationwith the LR34/Yr18 leaf rust/yellow rust gene inwheat, a gene that is impossible to detect by phe-notype or biochemical means. This developmentexemplifies the ideal of an integrated genetic ap-proach, in which specific processes at the genelevel are linked with whole plant physiology andfield assessments (Boote and Sinclair 2006; Cat-tivelli et al. 2008).

Ecosystem complexity—what itmeans for farm adaptation andplant breeding

Giampietro (1994) reminded scientists of the im-portance of considering the spatiotemporal scaleand complexity of agricultural ecosystems whenevaluating the likely impact of technological ad-vances. He used the green revolution in agricul-ture to warn about the consequences of “silverbullet” solutions—in this case, the simple fix ofnew rice and wheat genotypes, which producemore food for an expanding population. As notedabove, Swaminathan (2006) advocated greaterconsideration of the effects on land and waterresources, and on farmer equity of agriculturalinnovations such as new genotypes, higher ratesof fertilizer, and more crop protection chemi-

cals. Giampietro (1994) wrote about an addi-tional concern—the future danger of producingadditional food and sustaining additional peoplewithout considering the traditional cultural con-trol of food supply on the fertility of human popu-lations. Hence, it is important for plant scientiststo retain a perspective that plant breeding is butone of the disciplines that contributes to agricul-ture, and agriculture is but one disciplinary areain the landscape of human affairs on planet Earth.

The importance of the above perspective is il-lustrated by a list of developments in sustainablecrop production, produced by Crookston (2006)and his colleagues from the Crop Science So-ciety of America (Table 29.2). Improved cropgenetics is acknowledged as the number one fac-tor that has impacted on crop production and thisimpact is seen as unambiguously positive. In tworespects, the makeup of the #2–9 topics on thelist was interesting:

� The list illustrated the wide diversity of top-ics that are currently considered relevant byfarmers and scientists.

� Several topics remain controversial in termsof their positive and negative impacts onagriculture.

It is important that these examples of diver-sity and controversy are recalled when readingthe reviews in this book from crop specialists,who understandably take a “techno-positivist”approach rather than an “enviro-pessimist” ori-entation.

In summary, the emphasis of research intocrop improvement has evolved from a sin-gular or narrow focus on factors limitingpotential yield and production to one thatencompasses a production-environmental ap-proach, such as the adjustment of local agri-culture to climate change, the managementof agricultural systems and catchments toavoid physico-chemical imbalances (soil andwater pollution, nutrient exhaustion, acidifi-cation, salinization, air quality including theemission of greenhouse gases), improving the




Table 29.2. A “top 10” lista of the “most important developments and/or issues that had impacted on crop ecology,management, and quality during the past 50 years” – Crookston (2006).

Rank, developmentNumber of times

nominated Comments

1. Improved crop genetics, byconventional breeding orbioengineering

112 Comments on conventional plant breeding(embracing also the collection and storage of geneticresources) were universally positive. Comments onbioengineered crops were both positive andcautionary.

2. Substitution management—thereplacement of crop rotations andanimals with chemicals (nitrogenfertilizers, herbicides, andpesticides)

96 Many comments were positive but concern wasexpressed over the loss of biodiversity, the decline in“family farming,” and the inevitable emergence ofresistance to pesticides. N fertilizers and chemicalweed control received more “pro/con” commentsthan chemical control of insects/pathogens.

3. Government programs andpolicies

45 The impact of crop subsidy programs (eliminatingrotations and delaying rural adjustment) dominatedcomments. Also see 6.

4. The environmental movement,sustainable agriculture

43 The controversy concerning traditional andsustainable practices has shifted in the last 20 yearstoward an appreciation of public opinion and aprofessional acceptance of sustainable agriculture

5. Conservation tillage 40 Conservation tillage has increased the conservationof soil, time, energy, water, and carbon. CTcontributed much to the acceptance of sustainableagriculture but the dependency on chemicals hasincreased.

6. Changes in the operation of theLand Grant system of R, D, and E

35 Nostalgia remained among the older professionalsbut there was full acknowledgment of the shift in“power” from the public Land Grant system to thecurrent mix of public, industry (vertically integrated“big” agriculture), and agribusiness interests.

7. Precision technologies (GPS andGIS)

32 This technology received mixed reviews, with thechallenge to produce more agronomic benefits tomatch the appeal of GPS/GIS technologies tofarmers.

8. Improved mechanization 31 The wonderful but expensive array of power toolsand instruments has boosted farmer productivityand sustainable practices.

9. Improved water management 20 Most respondents came from arid States andirrigated regions, where competition for water andwater quality are already escalating issues.

10. Alternative crops (to cereals)and alternative uses for crops

18 The impact of alternative crops and alternativeusage of traditional crops was considered generallypositive but there were some negative responsesdirected against growing crops for fuel.

11–20. Miscellaneous, not listedabove

72 These topics included globalization, economicanalyses and modeling, demographics etc.

a415 crop specialists were contacted by email, and the 94 people who responded submitted a total of 545 nominations




adaptation of crops to environmental stressors(chemical, physical, and biological), and the on-going need to achieve improvements in cropwater-use efficiency and drought tolerance. Inpart, this evolution is a response to the ideason sustainable development espoused by au-thors such as Gordon Conway (productivity,stability, sustainability, and equity—Conway1986) and Jules Pretty (external costs ofagriculture—Pretty et al. 2000). In recent years,the research agenda has further broadened to in-clude environmental, financial, and social issueson the farm (e.g., Mason et al. 2003). Unfortu-nately, past research into on-farm business man-agement and off-farm supply chains has oftennot been relevant to farm profits (McCown andParton 2006) and, while the need for social indi-cators in agriculture is acknowledged, there areas yet no agreed protocols for the routine collec-tion of indicators that define the social capital offarm families.

Regional impacts of climatechange on crop production

Turning to specific impacts of climate changeon food production, a preliminary analysis byReidsma et al. (2010) of European crop andfarm production highlighted the importance ofadaptive capacity. This term was defined byReidsma et al. (2010) as the collective abil-ity of farms (determined by farm and farmercharacteristics) and regions (determined by bio-physical, socioeconomic, and policy factors) tocope with climate change by moderating poten-tial damages or taking advantage of emergingopportunities. For example, the impact of cli-mate change on a profitable crop (maize) grownon a productive soil type for cropping is likelyto be less than a less important crop (wheat)on a marginal soil type, since management willconcentrate yield-enhancing efforts on the mostresponsive situations. Within each European re-gion, farm performance varied according to farmintensity (i.e., use of fertilizer and crop protec-tion products, positive), farm size (i.e., economic

size, positive), and arable land use (i.e., grass-land and permanent cropping area had a neg-ative impact). Broadly, the study confirmed alower generic capacity and a greater sensitiv-ity to climate change in Mediterranean than innorthern regions. However, there were a numberof region by factor interactions—for example,in France and the United Kingdom, a large eco-nomic size increased the negative effects of hightemperatures, whereas in other regions the influ-ence was small. Reidsma et al. (2010) concludedthat the impacts of climate on crop yields can-not directly be translated to impacts on farmers’income, since farmers adapt by changing croprotations and inputs, and governments may in-tervene by adjusting crop subsidies or researchpolicies. They recommended that frameworks toassess the effectiveness of adaptation strategiesshould start with an appreciation of stakeholders’perspectives rather than from a narrow biophys-ical modeling approach. These broad findingsand conclusions were in line with the earlierstudy by Olesen and Bindi (2002), who sug-gested a number of resource-based policies tosupport flexibility in the adaptation of Europeanagriculture to climate change. Their list of poli-cies embraced land, water, nutrients, agrochem-icals, energy, genetic diversity (which, with newgenotypes, provides plant breeders with impor-tant basic material for adapting crop species tochanging climatic conditions), research capacity,information systems, and culture.

For example, the analysis by Seo and Men-dohlson (2008) of South American farmers pre-dicted that choice among the seven most pop-ular crops varies with climate. Farms that arecooler are more likely to choose potatoes andwheat, average temperature (18◦C) farms tendto choose maize, soybeans, and rice, and farmsin warm locations choose fruits, green vegeta-bles, and squash. Similarly, farms in dry loca-tions tend to choose maize and potatoes, farmsin moderately dry conditions tend to pick soy-beans and wheat, and farms in wet conditionschoose fruits and vegetables, squash, and rice.The authors of this report mentioned that the




predicted responses in South America wereconsistent with the response functions from asimilar study undertaken by their team in Africa.

Perhaps the most profoundly threatened crop-ping systems are those in the delta regions ofmajor rivers (e.g., the Guadalquivir in Spain, theNile in Egypt, the Ganges in West Bengal andBangladesh, the Mekong in Vietnam, and theHuang He in China). The area and productivityof croplands on these low-lying areas are vulner-able to the impacts of both flooding and salinity,as mentioned in Chapter 12 of this book.

In summary, farmers will adapt their pro-duction systems to climate change, perhaps bymodifying their enterprises (e.g., in mixed farm-ing systems, toward more livestock productionor crop production depending on the climatictrend), by changing the crop and pasture speciesthat they sow, and/or by adjusting the timingof crop operations. Whether the future climatefavors human habitation and food production(e.g., northern Europe) or increases the vulner-ability of already stressed regions, for examplein river deltas (above) or in arid central Asia(Lioubimtseva and Henebry 2009), plant breed-ing must be linked with other disciplines, espe-cially agronomy (Ingram et al. 2008; Luo et al.2009) in order to be part of the solution. For thediscipline of plant breeding itself, the policies ofrural R&D agencies, governments, and privateinvestors are likely to be crucial to the level anddirection of future efforts.

Conclusions for progress in plantscience—future opportunities

In a global economy, there are several influencesthat will determine the capacity of plant breed-ers to cope with climate change. On the demandside is the upward trend in world population andthe increasing numbers of relatively affluent con-sumers, factors that will positively affect the sizeof the global market for food. On the supplyside are potentially negative impacts, includingclimate change, the availability of essential agri-cultural inputs such as fertilizer, chemicals and

energy, and the policies of governments, insti-tutions and corporations. Future perturbations toworld agriculture arising from progressive cli-mate change or sudden input shortages (fuel, fer-tilizer, chemicals) may interact with agroecosys-tem types or government policies, and triggermajor changes to agricultural industries.

In recent years, research institutions haveexperienced shifts in the policies of gov-ernments and foundations who, noting thedecline in the proportion (2.5%) of gross na-tional product contributed by agriculture, havefailed to adjust production levies and grantsto counter the apparently declining pool of re-search funds available for food production re-search. Hence, governments are spending lesson agricultural research at a time when re-search costs are escalating. Government de-partments, bureaus, and universities also offercontract rather than tenured employmentto scientists and other professional researchers.These negative trends may limit future gainsfrom agricultural research. More optimistically,they could be balanced by (1) better access toand communication with agricultural scientistsaround the world, thereby facilitating “spill-in”benefits, and (2) improved collaboration betweenproduction scientists and environmental scien-tists. Another issue, the nonadoption or slowadoption of research findings, especially withcomplex technologies that are aligned with sus-tainable production, is being addressed throughthe use of participatory extension methodologies(e.g., Pannell et al. 2006) rather than employingthe diffusion (trickle down) approach that is ef-fective with simple technologies.

Predictions of hotter continents with a moreerratic climate may bring greater operational di-versity in agriculture, at least at the regional level.Resource limitations and other constraints mayencourage some producers to seek a lower in-put, more ecologically focused production sys-tem rather than one that operates at a higherlevel of production risk. Animal producers maymake greater use of perennial pasture species,supplemented strategically with annual species,




to convert rainfall to fodder and meat and toprotect the soil resource. In cropping zones, riskycrop production areas may be turned over tomeat and wool production (Kopke et al. 2008),while crops may extend further into suitablehigh-rainfall areas (Harle et al. 2007) and higherlatitudes (Olesen and Bindi 2002). As well, thestrong demand for food may lead to a greaternumber of larger, specialized farms that achievesynergy through integration with complemen-tary businesses (e.g., crop farms with feedlotsor chicken farms). The complexity of managinglarge, mixed (crop + livestock) farms may beoffset through innovative business partnershipsthat not only retain mixed farming (diversifica-tion) but also encourage simultaneous specializa-tion, essentially by separating the managementof crops and livestock and placing each enter-prise into the hands of enthusiasts. For example, afarmer specializing in crop production may workwith an agribusiness expert to plan and imple-ment crop rotations, and with a well-organizedlivestock specialist who could run herds/flockson several farms to utilize crop residues and per-manent pastures.

While considerable benefits may come frominnovation in the economic and social aspectsof agriculture, there will be an acute need torefine the technology of production in order tocope with heat stress, drought, rising sea levels,and resource constraints. The role and successof the plant breeder in food production, sup-ported by geneticists, physiologists, statisticians,agronomists, and farmers, is pivotal.

The “bottom line” for food production in2050, a crucial time when the population peakwill meet a possible zenith in climate change,is probably determined already. It is profoundlydifficult to accelerate progress toward this crisisdue to the time lags that are involved in crankingup scientific research to boost food productionsystems (Keating and Carberry 2010). Althoughcrop yield potentials will continue to move incre-mentally upward, it is likely that political inertia,knowledge barriers, and human selfishness willconstrain the rate of crop improvement to a level

that is insufficient to feed the world, unless thereare concomitant reforms in food distribution andutilization.

Endnote

1. In 1975, I discussed this topic with Dr Albert Pugsley,the then Director of the Agricultural Research Institute inWagga Wagga (Australia), shortly after his return from avisit to the Northern Hemisphere. At the time in Australia,following the release of several reduced height wheat cul-tivars, there were many cereal breeders whose work wasmore independent than it is today.

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